Outboard motor unit having hydraulic jet propulsion means



Feb. 22, 1955 w. H. TINKER 2,702,516

OUTBOARD MOTOR UNIT HAVING HYDRAULIC JET PROPULSON MEANS Filed May 2, 1952 2 Sheets-Sheet l INVENTOR.. WALTER H. TINKER Feb. 22, 1955 w. H. TINKER 2,702,516

OUTBOARD MOTOR UNIT HAVING HYDRAULIC JET PROPULSON MEANS Filed May 2, 1952 2 Sheets-Sheet 2 INVENTOR.

WALTER H. TINKER United States Patent O" OUTBOARD MOTOR UNIT HAVING HYDRAULIC JET PROPULSION MEANS Walter H. Tinker, Cincinnati, Ohio Application May 2, 1952 Serial No. 285,751

8 Claims. (Cl. 115-16) This invention relates to improvements in liquid displacement methods and means, and more particularly to such improvements as applied to the propulsion of boats and the like, but without limitation to such field of usage.

The usual open marine propeller has, despite many years of acceptance, proven to be a relatively inefficient driving agency under all practical circumstances when applied to boats and vessels of various types, notwithstanding its inherent high mass-to-velocity ratio. This is true by reason of supposedly unavoidable and hence accepted, displacement effects of an order not usefully applied as propulsive thrust; for example, the conventional marine propeller, whether small or large,

.exhibits many undesirable turbulence or cavitation effects as a result of which much of the circumjacent liquid is agitated without useful driving effect. Numerous attempts have been made in the field of propulsive displacement along the lines of propeller enclosures of various types, and along the lines of adaptation of more or less conventional centrifugal pumps to the propulsion field. Some of these efforts have, but with indiiferent success, overcome in part the shortcomings of conventional screw propellers. The present improvements accordingly have as a major and general object, the increase in efficiency of conversion of power applied to a drive shaft, as translated to effective forward thrust of a boat or vessel, this object being achieved particularly through a substantial reduction in non-useful displacement and by reason of minimization of adverse cavitation throughout the displacement system.

In order objectively to state the general method identified with the present improvements, there is effected a diffusion of a liquid intake stream with a marked reductionin its velocity in the entering portion of'the displacement system, which velocity reduction serves markedly to reduce friction and cavitation losses; such reduction of velocity and minimization of these losses results in some energy inherently reflected in propulsive thrust, instead of turbulent losses in usual intake elbows. The intake stream, following its relative deceleration, is thereupon gently diverted in its course so as to impart thereto a certain degree of preliminary rotation in advance of introduction of the intake stream to a rtary impeller, all with the object of conserving energy in the intake stream, and resulting further in a minimization of rate of acceleration of the liquid when attacked by the impeller. Furthermore, since in a propulsion unit of the type under consideration the energy in the inlet flow may represent a very substantial portion of the overall energy content of the propulsive jet, the described steps of conserving initial energy importantly contribute to the maximum increase in propulsive thrust.

A further objective which. may be realized through the presently improved displacement unit, consists in a facility for the utilization of multiple impellers and flow systems, depending upon the head-mass relation desired.

Yet another object of the invention is realized, somewhat akin to the advantages noted, in that, in a system embodying a plurality of displacement units and flow systems, a multiple displacement device lends itself to enclosure in a casing the proportions of which make for improved overall streamlining and appearance, with a minimal resistance when used as.a submerged propulsion unit.

A still further and highly important object of the fore generally mentioned.

2,702,516 Patented Feb. 22, 1955 2 invention is realized in a design such that, whether a single, double or other multiple displacement unit be employed, all of the frontal area of the unit is available vto receive intake flow, and thus to minimize head resistance. Similarly as akin to this object, it is noted that the overall design is such that the entire rear area of the unit is available for a discharge stream, by reason ice of which and consistent with the underlying principles of the device, a larger volume of liquid, impelled at a lesser velocity, achieves with much less frictional and turbulence losses, a given predetermined thrust value.

Yet a further object of a highly practical nature is realized in a novel mounting, arrangement and structure of enclosing casing sections, together with a sectional arrangement of deck elements, interpal partition elements, and in fact if desired, all of those parts internal of the casing walls which control the how of liquid 'through the system. This object is by preference realized in a sectional casing structure in which may be rotatively gupported one or more impellers and access to all parts of such frame or cage being had upon septions. The provision covered by the present object is of particular advantage in production in that it simplifies coring practice, internal cleaning, grinding and other operations usually necessitated under dilficulties as in many types of centrifugal pumps and the like.

A still further, and by no means the least important objective feature of present design, is realized in an improved type of impeller which, although same may be usually referred to as of mixed fiow type, is nevertheless to an important degree of an axial flow characteristic. The improved impeller possesses an arrangement of hub and vanes such that its displacement is predominantly in a direction axially of the impeller, in the inlet region and predominantly radial at the outlet periphery, and results. objectively in a design of rotary displacement member which is particularly advantageous when used in a flow system of the type hereto- The foregoing and numerous other objects will more clearly appear from the following detailed description of an exemplary embodiment of the invention, particularly when considered in connection with the accom panying drawings, in which:

Fig. 1 is a side elevational view of a small propulsive unit embodying the present improvements, and as operatively connected to and supported by an outboard motor assembly which latter is or may be of conventional type, 'as illustrated;

Fig. 2 is a frontal elevation partly in section, of the submerged propulsion unit such as shown in Fig. l, a

minor portion of Fig. 2 being shown in section;

Fig. 3 is a vertical sectional elevation, with sectional portions taken along line 3-3 of Fig. 2;

Fig. 4 is a horizontal sectional view with parts in elevation, the sectional portions being taken along staggered planes as indicated by line 4-4 of Fig. 3; and

Fig. 5 is a horizontal sectional view with certain parts in elevation, the sectional portions being taken along a staggered section line 5-5 of Fig. 3.

Referring now by characters of reference to the drawing, it is noted that the engine and tank assembly generally indicated at E, is attached through the usual swivel connection to a clamp C, and for steering purposes is provided with a retractible control arm or tiller T. It will be well understood that in a hollow column HC is a vertical drive shaft DS (a portion of which is shown by Fig. 3), which constitutes a power source for the displacement unit to be described, and which in Fig. 1 is generally indicated at 10.- The unit 10, as shown, normally operates in submerged relation.

The unit 10 includes an enclosing casing or housing consisting in the present example of a pair of sections or housing components generally indicated at 11 and 12, these including external Wall members and which collectively provide a full enclosure for the parts located internally of the casing. The housing 11--12 parts along a fore and aft median plane 13, and includes in addition to side wall elements 15 and 16, top closure portions 17 and bottom closure wall portions 20. The sides l6 of the sectional enclosure, include relatively heavy boss portions 21 formed on and as a part of the lateral walls 15-16, the portions 21 being cored or drilled to provide horizontal bolt passages therethrough as indicated at 22 for the reception of assembly bolts 23.

Extended as a portion of a partly internal, partly external frame or cage to be described, and above the top portions 17 of the casing, is a boss shown at 24, and over which is disposed an uppermost projecting portion or plate 25 extended conformingly into the lower end of the hollow column HQ. The latter is provided with a pe ripheral mounting flange 26 interfitting a conforming surface on the top of plate 25, and assembled to the latter and to the boss as by screws 27. A similar boss or projection 24 is noted at the bottom of the assembly, these being interconnected by vertical ribs or flanges 29 and 30, at the front and rear of the assembly.

Proceeding now to a description of the parts located internally of the casing proper, reference should first be made to the virtually fully open frontal area of the unit as will appear from Fig. 2, in which it will be seen that,

'tically no head resistance is encountered, and at the same time, relative motion between the unit 10 and the ambient water is established concurrently with the introduction of the liquid to the intake portion of the system. The open front of the casing structure may be said to constitute a large intake area 31, comprised of separate intake ports 33, 60 and 33', later described.

As will best appear from Fig. 4, the entire rear area of the unit is similarly open for discharge, and the opening in this location may be referred to as a discharge port 32 (Fig. 4).

In the arrangement illustrated, two actual displacement units and substantially separate flow systems are utilized. These are arranged within the casing l5-16 in an overand-under relation, with the two displacement units vertically spaced, but with the two units virtually identical, although relatively reversed or transposed. Since the two units are or may be, but for this transposition, constituted of identical elements, a description of one will sufiice for both, the parts of the lowermost such unit being identified by prime reference characters.

In the uppermost unit a portion of the large intake port 31 constitutes a separate intake port for the upper displacement unit, which portion is particularly indicated at 33, and it is through this port that the intake stream is directed to, thence through an intake passage 34. As will readily appear from Fig. 4, the width of the intake passage quite materially exceeds, in fact is shown as several times as great in dimension as, the diameter of the impeller, the latter being later described in detail. Thus the intake passage 34, and for similar reasons the discharge passage from the impeller of this unit as will appear, is of a horizontally flattened aspect, exhibiting a much greater sectional area in any cross section of intake passage, than the area,of,the impeller circle, as will appear, the same being1 likewise true of the discharge passage as will be note It is preferred to reduce the velocity of the intake liquid btween the port 33 and the impeller serving the unit, this latter being generally designated at 35. In Fig. 3 it will appear that the intake passage is of progressively greater depth between the port 33 and the impeller 35, thus resulting in a desirable diffusion in this area, with an appreciable reduction of relative velocity of the intake stream and the unit. inwardly of the intake port, followed by acceleration of the intake stream as same approaches the impeller. Acceleration of intake flow reaches a maximum at the very inlet to the impeller. thereby keeping the impellet diameter at a minimum value.

The discharge passage beyond the impeller 35 will directly appear in the right hand portion of Fig. 4, from which it is seen that the same cross-sectional characteristics referred to in connection with the intake passage 34.

likewise prevail in the discharge passage of the unit, in-

dicated at 36.

Although final enclosure of the displacement zone and the intake and discharge passages characterizing each displacement unit, is completed by the sections or components of the outer casing, it may be noted for structural completeness that the uppermost unit is partly defined by an upper deck element 40 spaced somewhat above a lower deck element 41 and between which are defined the intake passage and a portion of the displacement zone identified with the region immediately about and surrounding the impeller 35. The central region of the deck element 40 is characterized by a depending circular element 42, which as shown, may be separate from deck 40, and which is of a generally inverted frusto-conical shape, although departing from a true conical surface in that it is of a concave external pattern conforming generally in curvature to the concave portion of the impeller hub, later described. Internally of the boss 42 is a cylindrical shaft-receiving journal supporting portion 43, and through which the impeller shaft of the unit operatively extends. The metal in the region of boss 42 and portion 43 is extended outwardly to form the portion 24. Similarly downwardly extended from member 42 is a neck 43, merging into the bottom boss 24.

Formed integrally with one or both of the deck elements 4041 and bridgingly spaced therebetween in vertical planes in the example shown, is a series of inlet-directing vanes, the larger of which are indicated at 44 (Fig. 4). and generally parallel to the right and left hand vanes 44. are correspondingly curved but shorter vanes appearing in order as 44A, 44B, 44C, 44D and 44E, in greater or less number in each such series, as required. It will be noted that cacch of the vanes 44 et seq. if produced, will distinctly intersect the impeller circle; further that each has, structurally considered, a point of origin close to the intake periphery of the impeller 35, thence extending outwardly in a direction such as to direct the flow of intake liquid by gradual deflection, somewhat tangentially into the intake periphery of the impeller. It is distinctly desired to avoid abrupt changes in direction of flow in the regions of the several vanes 44 et seq., these vanes serving collectively, to impart a starting rotation of intake stream and a gradual directioning of the stream into the full, or substantially the full periphery of the intake zone of the impeller. In the example shown, the'deck elements 40, 41, 40' and 41' are formed in half portions, each carrying one set of the adjacent vanes, these halves being formed as portions of the casing halves 11 and 12, extending inwardly thereof to meet along a fore-aft plane 13.

The deck and partition elements of each of the displacement units further include, as exemplified in the upper unit, a third deck 50 spaced below the deck 41, so that the decks 50 and 41 coact, with the outer casing sections, in defining a discharge zone originating by preference fully about the discharge periphery of the impeller, and thence extended interiorly and rearwardly of the assembly, it being noted that the innermost portion of the discharge passage 36 is defined in part by a large partition element of increasing curvature indicated at 51 (Fig. 5). This volute-forming element may be said to have its point of origin 52 close to one side of the periphery of the discharge region of the impeller 35, thence to extend 'with increasing curvature to a point generally diametrically opposite point 52, the relation of the member 51 to the impeller being somewhat similar to the conventional volute. An auxiliary element generally similarly curved, is located inwardly of member 51 and is designated at 53. Curved somewhat oppositely of the elements 51 and 53 and located aft of these elements in the discharge passage, is a series (shown as three) of oppositely curved vanes or discharge-directing members designated at 54, 54A and 548. It will have appeared that the normal tendency of the volute arrangement of parts 51 and 53 will be to result in an appreciable lateral thrust on one side of the discharge passage. Besides the de sirable straightening effect on the discharge stream, the inversely curved vanes 54 et seq. serve to impart, gradually and virtually without turbulence, a straightening effect of the discharge stream and thus to minimize any lateral thrust effect as aforesaid. It may at this point he noted that, since the lowermost displacement unit is relatively inverted. to whatever extent a dominant lateral thrust exists in either unit, same is virtually compensated for. or neutralized by an opposite effect of the companion unit. Also, the flow leaving the impeller remains sub stantially in a velocity slate" and the usual velocity to pressure and back to velocity as with the usual volute with attendant losses, is avoided by the present arrangement.

It has been heretofore noted that, as shown, the deck and internal partition elements 40, 41, 44 et seq., 51, 53 and 54 et seq. all constitute parts of the halves of the casing structure. Thus, when the outer casing sections are removed, the passages and vanes constituted by these elements are laterally open and are all readily accessible for cleaning, grinding and the like, and are likewise fully open for inspection or manual access at any time with obvious advantages.

It will be seen from Fig. 5 that deck elements 50 and 50' are, in the present example of one piece construction, including the vanes 51, 51 and others carried thereby. Thus these decks are not medially divided. Each of the decks 50, 50 is provided with a circular opening 50A for assembly purposes, and is supported in the casing by welding at spaced points, or by other means, such as interengagement of the deck margins in slots 5013 (Fig. 3). Similar half-circular openings, about the impellers, are provided in deck elements 41 and 41.

Although in small displacement units requiring only low'thrust values, a single such unit as that described is adequate, the dual unit illustrated offers certain distinct advantages. Among these is a better proportioning of the whole structure for streamlining and minimization of external flow resistance. This result is still further enhanced by the provision of a substantial, intermediate fore and aft flow passage between the two propulsion units. Such a passage in the present example includes a large inlet port 60, which together with the ports 33 and 33 accounts for virtually all of the frontal area of the assembly. Inwardly of the port 60 the elongate longitudinal passage formed between the decks 50 and 50', proceeds into a somewhat restricted portion 61, thence rearwardly through a portion of substantially even cross section indicated at 62. The passage 61-62 is virtually the full width of the casing interior, between its entering throat and its zone of discharge. As will now be obvious the fiow through passage 62 will be directed virtually in a straight line, and the discharge therefrom is induced or aided by the discharge streams respectively above and below that from passage 62, and emanating from the upper and lower displacement units.

Further in respect to the frame or cage structure and parts directly carried thereby, it is noted for completeness that the drive shaft in the unit proper, designated at 65, terminates at its upper end in a female splined portion 66, permitting a quick slidable connection between the shaft DS and the shaft 65. The splined socket 66 is located in an upper head formed on shaft 65, the head being indicated at 67 and journalled in a bearing member or bushing 70, which latter is seated in the central region of boss 24 on the cage or frame. A corresponding and similarly mounted element 71 is located at the lower end of the shaft 65 and seated in boss 24. The shaft bushing or journal elements 70 and 71, may be formed of metal, rubber or the like, and water-lubricated. Final assembly of shaft 65 and its associated journal elements including a bushing member 72, is efiected, as later described, through an assembly nut 73 at the bottom of the shaft. Shaft 65 is provided over the necessary portion of its length with a keyway 75 serving to receive impeller keys by which the impellers 35 and 35 are attached to the shaft. Thus it will haveappeared that the impellers, shaft 65 and certain of the deck and vane elements may be fully assembled and adjusted, all in operative relation upon application of the outer enclosing casing sections. Even before assembly of the casing sections, the cage andcontents may be attached for inspection, to parts HC, 26 and shaft DS for rotative observation.

Proceeding now to a description of the preferred form of impeller and the structural features of its hub and vanes, as will be observed from Fig. 3, the hub 80 is of an even diameter over a substantial part of its inlet region, being that portion above the deck 41 in Fig. 3. Below such even diameter portion, the hub is gradually increased in diameter substantially throughout its remaining axial length. The hub, except for its uppermost region, may be referred to as of a substantially frusto-conical form, but modified in that its lower region is exteriorly of a concave aspect in which region its diameters gradually increase almost fully downwardly to a circular base plate portion 81. The hub 80, as will now be obvious, is provided with an axial shaft-receiving bore to accommodate the shaft-65, the impeller being provided with a shaft key 75A coacting with the keyway in the hub (not shown), and likewise engaging the keyway 75 in the shaft 65.

Each of the impellers is shown (but without limitation to any practical number) as provided with four vanes equiangularly spaced about the hub 80. Each such vane is of a somewhat spiral aspect, and each is carried by and attached to the hub 80 along the inner vane margin, the several vanes being indicated at 62. The leading edge of each vane indicated at 83 is a linear edge, bearing an acute angle relation to the axis of the impeller and such edge is of proper pitch along its length. Each vane is, by reason or the taper of the hub, of a varying, particularly a diminishing width below the intake portion of the impeller. Likewise, each vane eXhibits a diminishing pitch between its leading edge 83 and its trailing edge ea. It will be observed that, considering each vane or blade in respect to its own longitudinal median line, the vane is given a pronounced twist from leading to trailing end. Also, the trailing margin proper of the blade is joined to the largest diameter portion of the impeller, so that in the present example, rather than resulting in the delivery of fluid straight ofi of the trailing vane end, there results a distinct pocket in this region compelling a gradual, lowturbulent delivery from the end of each blade outwardly of the peripheral portion of the impeller close to the base disc 81 thereof, in a vectorial combination of radial and peripheral directions. As the impeller is rotated, the liquid supplied fully peripherally of the intake region is picked up by the leading margins 83 thence by gradual, predominantly or at least pronouncedly axial displacement, moved downwardly by the blade and outwardly by the larger diameter portion of the impeller in the outlet zone. As an aid to the non-turbulent entrance of the liquid to the inlet portion of the impeller, it will be noted that the widely concave curvature of the portion 42 formed on or carried by the upper deck element 40, will serve to direct the incoming liquid from passage 34 almost axially into the impeller intake region, modified by whatever degree of rotation is supplied by members 44.

The impeller as will be seen, is of substantially axial length, and thus, with adjacent elements, serves to define a displacement Zone which may be referred to as cylindrical in its boundaries, the axial length of such cylindrical zone being that of the impeller, and the diameter of the displacement zone being that of the impeller circle, which latter may be described as the diameter of the disc or base portion 81.

Reference will now be made to the manner of assembly of those internal elements which are associated with the cage or frame, and which may be considered as a subassernbly, susceptible of completion or substantial completion, on the bench and under conditions of easy manual access and opportunity for visual observation of all normally internal parts. This sub-assembly is best effected from the top to the bottom of the unit as shown by Fig. 3, and will involve the insertion of the shaft 65 w th the shaft-carried portion 67 in the element 70. Then, with these parts inverted, the circular, somewhat conical element 42 is set in place, followed by insertion of impeller 35 over the shaft, with its key in the keyway. The circular base 81 of the impeller may now receive a spacer 85, followed by impeller 35', with its key properly located in the shaft and hub keyways. The element 42', followed by bushing 72 will complete the assembly of the rotative elements upon the application of nut 73 when threaded up on the lower end of shaft 65. It may here be noted that the circular openings in each of the deck structures 50 and 50 are adequate in area to permit their passage over the shaft carried elements in the proper relation thereto. The deck elements 50, 50' may at the time of final assembly be definitely positioned as by the interfittmg of their margins into the adjacent outer elements for example, one such margin shown as indicated at 5013 (Fig. 3), extending into a notch in member 30.

It has heretofore been noted that the remaining deck and vane elements are carried by the detachable halves of the exterior casing structure. These latter may now be laterally applied, one from each side of the sub-assembly described, and secured into place by means of the transverse bolts 23. It is here noted that the several half deck elements carried by the detachable casing sections, are provided at one or both ends, with notches or half notches, which accommodate and embrace the vertical flanges 29 and 30. these latter thus serving in assembly to stabilize and position the divided deck portions.

The spacer or bushing 85. briefly referred to, is provided to assure an even separation and spacing of the base plates 81 and 81 of the two impellers. This element surrounds the shaft 65 in this intermediate zone. and will of course rotate with the shaft and the two impellers.

The mode of assembly of parts of the cage as described. presupposes that the deck elements 40, 41 and 50, and 1h, 41 and 50', are individually formed. It is however contemplated that any plurality of the decks of each displacement unit may be inte rally formed, as by casting, with reduction in number of parts and some simplification of assembly.

Sufiicient description of function has heretofore been included in a discussion of the structural elements to render the general principle and method of operation fully apparent. but it may be noted for completeness that. assuming the engine to be in operation and applied to a boat for propu sion thereof, the unit 10 Will be impelted forwardly. This forward motion of the unit with respect to the ambient water. results in a positive intake of water at substan ially the velocity of the boat. through the intake ports, filling that portion of the intake passage forwardly of the vanes 44. As the intake stream progresses throu h assa e 34, same will be deflected by vanes 44D and ME. the intermediate portions by vanes ellC. and the outermost portions of the stream similarly gradua ly diverted thr u h an an le somewhat greater than 90 degrees and fed into the intake region of the impeller substantially over the full periphery thereof. During the time of movement of the intake stream through passa e 34. since the passa e is of increasing de th toward the impeller and of increasing width (see Fig. 4)

. in the same re ion. there will result a marked reduction in velocity of the in ake stream relative to the unit prior to its induction by the impeller inlet region. Themovemerit of liquid throu h the disp acement zone. as will have appeared, althou h there is necessarily an outward or centrifugal com nent, takes place to an important degree in an axial direction as impelled by the vanes, with an outward deflecti n ,by the tapered hub 80 into the dischar e zone. The velocity of liquid through the displacement zone is of course augmented, but delivery therefrom into the discharge passage takes place in an orderly manner relatively free of turbulence-cavitation effects. S me diffusion and reduction of velocity again occurs in he volute portion about the impeller discharge and specifically within the confines of vane element 5], but mainly the velocity is directed for thrust production. Beyond vane 51. the vanes 54, 54A and 548 will exhibit a straightening efiect on the discharge stream, said deflection augmenting thrustand gradually diverting and directing the flow in this region to a fore-aft course outwardly through the discharge passa e 36.

It has been noted. and will readily be observed from Fig. 3, that the impeller 35 of. the lower displacement unit, and the related wall elements associated therewith as well as the vanes. are inverted relative to the corresponding elements of the uppermost unitv Thus it will be seen from Fig. 3 that, looking downwardly along shafts DS and 65. impeller 35 will rotate in a counterclockwise direction. displacing liquid downwardly through the unit as shown, and outwardly into discharge passage 36. The lower impeller 35', necessarily rotating in the same direction as and concurrently with impeller 35, will displace the liquid upwardly from the intake to the discharge passage and outwardly through passage 36. By reason of the extraordinarily large intake passa es 34, 34', and the same general magnitude of the discharge passages beyond the respective impellers. coupled with the fact of reduction in velocity and diffusion of the incoming stream. there results a markedly lessened extent of turbulence and other unfruitful displacement. and thus these features make for a highly efficient unit. The feature of virtual avoidance of head resistence. and likewise the virtual avoidance of drag by utilization of the full rear area of the unit for discharge purposes. still l'urther enhances overall efliciencv particularly when the assembly is utilized for propulsion purposes. This result is materially enhanced by the provision of the lar e fore-aft passage 62 which permits of free movement of the liquid otherwise frontally displaced. and the discharge of liquid through this passage in flowindlucsilsig relation to the discharges of the impellers 35 an The description of features of design and elements of structure of the present displacement unit, will have revealed a marked departure from earlier submerged displacement devices, particularly in that all flow passages through the unit and even through the displacement zone proper, are designed to move a relatively large volume of liquid at a relatively low velocity, with minimal frictional losses, and with minimal pressures through all parts of the flow system. At no point in the system need these pressures exceed the order of 2-4 p. s. i. Furthermore, the underlying principles of the present arrangement, operating as it does on a low head, large volume principle, require energy values of only a low order per pound of liquid moved through the system. It may further be noted that any leakage tendencies are minimized by reason of the low pressures involved. Also, from the foregoing explanation it will appear axiomatic that the lower order of pressures existing throughout the system, minimizes material requirements in most parts of the unit.

It will now have appeared that the arrangement described will serve fully to realize each of the several objects hereinabove stated, and others implied from the description of structure, and principles of operation. Al though the invention has been described by particularized reference to a selected embodiment, the detail of description should be understood in an instructive, 'ather than in any limiting sense, numerous variants being possible within the fair scope of the claims hereunto appended.

I claim as my invention:

1. An outboard motor unit for propelling boats comprising a motor, a casing including external and internal wall elements formed to provide a frontal intake port with an intake passage extended rearwardly of the intake port, said intake passage being increasingly expanded along its length, whereby to reduce appreciably the velocity of the intake liquid flow, a drive shaft connected with said motor for rotation thereby and extending into said casing for rotation relative thereto, a rotatable im peller fixed on said drive shaft within said casing, said intake passage providing an intake region substantially around the impeller, the casing being formed to provide a discharge passage and port beyond the impeller, and a series of spaced inlet-directing vanes located in the line of inlet flow just ahead of the impeller each saidvane being broadly curved and the vanes collectively arranged to direct intake liquid flow tangentially into a major portion of the periphery of the impeller intake region in the direction of rotation of said impeller.

2. An outboard motor unit for propelling boats comprising a motor, a casing characterized by external and internal wall elements formed to provide a separate intake passage and discharge passage, a drive shaft connected with said motor for rotation thereby and extending into said casing for rotation relative thereto, a rotatable impeller fixed on said drive shaft within the casing, the impeller being of a substantial axial dimension and of mixed flow characteristic, with axial portions of the impeller located on opposite sides of one of the internal wall elements, one axial portion of the impeller opening into the intake passage, the other axial portion opening into the discharge passage, a plurality of widely curved, inlet-directing vanes located in said intake passage proximate the impeller and carried by one side of said internal wall element, said intake vanes being arranged to direct flow in the direction of impeller rotation and tangentially into a major portion of the periphery of that impeller portion on the side of the wall element by which the intake vanes are carried, and a partition element carried by the opposite side of the last said wall element, the partition element being curved as a volute element from a point of initiation close to the periphery of the impeller on the discharge side of the last said wall element, the partition element thence continuing with increasing spacing from the impeller in the direction of impeller discharge. and a reversely curved, discharge-directing vane located beyond the said volute defining element, the casing being provided with a discharge port at the terminus of the discharge passage and beyond the last said vane.

3. Apparatus for propelling boats comprising a motor, a casing provided with fore and aft openings sewing as intake and discharge ports respectively, a pair of displacement units within said casing, each said unit including stationary wall and partition elements internally of the casing and forming therewith, a forwardly located intake passage, a displacement zone, and a discharge passage extending rearwardly from the displacement zone, an impeller rotatably mounted in the displacement zone of each of said displacement units, a vertical impeller shaft common to the two impellers, and extended depthwise of the unit and being connected to said motor for rotation thereby, the two displacement units being relatively physically reversed and spaced one above the other, the casing being formed to provide an induction passage between said units, said induction passage including a rearwardly converging intake portion proximate to the intake passages of said units and a discharge portion which joins the discharge passages of said units forwardly of the rear end of said casing.

4. Apparatus for propelling boats comprising a motor, a casing, a drive shaft connected to said motor and extending into said casing for rotation relative thereto, and a rotary impeller fixed to said drive shaft within the casing, the impeller being of mixed fiow type, but being dominantly of an axial displacement characteristic and of substantial axial length, elements internal of the casing formed to provide a large volume intake passage directed to and substantially fully surrounding one axial portion of the impeller as an intake region, the casing and elements therein further being formed to provide a large volume discharge passage initiated about substantially the full periphery of a discharge region of the impeller spaced axially of the said intake region, the impeller being characterized by a substantially frusto-conical hub, and vane elements wrapped about the hub and each pitchedfrom its leading end to its trailing end in adirection from inlet to outlet regions of the impeller, the hub and vane elements coacting to direct the liquid radially outward into said discharge passage, the casing elements including a stationary partition provided with a circular aperture within which the impeller rotates, said partition serving to separate the said intake region and outlet region of the internal casing elements and the impeller.

5. A device for propelling fluid comprising an impeller and a housing, said housing having a stepped fore and aft channel extending therethrough including a rearwardly diverging inlet passage portion, a vertically extending impeller chamber portion and a rearwardly extending discharge portion. means in said inlet passage portion for imparting a prerotation in the direction of impeller rotation to the liquid passing toward said impeller, the inner end of the inlet portion being closed by a circumferentially extending vertical wall for directing the fluid into the inlet end of the impeller chamber, a vertical shaft extending into said impeller chamber and rotatably mounted in said housing, said impeller being mounted on said shaft for transmitting fluid axially and radially through said impeller chamber, said impeller having an inlet disposed adjacent the inner end of the inlet portion, a vertical wall extending about the impeller and forming the impeller chamber and a closure for the forward end of the discharge passage, vertically extending arcuate diffuser vanes in said discharge portion, a second channel in said housing extending in a fore and aft direction adjacent said first channel, said channels having a common discharge whereby fluid discharge from the discharge portion of the first channel will entrain fluid from the second channel and discharge the same through the common outlet.

6. An outboard motor unit for propelling boats comprising a motor, a casing including external and internal wall portions, a drive shaft connected with said motor for rotation thereby and extending into said casing for rotation relative thereto, and an impeller fixed on said drive shaft internally of'said casing, said casing wall portions being arranged to define an intake passage for directing liquid from an intake port at the front end of said casing rearwardly to said impeller, a discharge passage for directing the liquid from the impeller rearwardly to an outlet port at the rear end of said casing, and an induction passage leading from the front end of said casing rearwardly and joining the discharge passage, the wall of said induction passage adjacent said intake passage being curved rearwardly toward the axis of said induction passage so as to cause the creation of a negative pressure on the front end of said unit.

7. An outboard motor unit for propelling boats comprising a motor, a housing adapted to be submerged in the water, said housing being provided with a stepped fore and aft channel extending therethrough including a rear wardly extending intake passage portion having a gradually increasing transverse cross sectional area so as to reduce the velocity of the water flowing therethrough, a vertically extending impeller chamber portion and a rearwardly extending discharge passage portion, a generally vertical drive shaft connected with said motor for rotation thereby and extending into said impeller chamber portion for rotation relative thereto, an impeller mounted on said drive shaft in said impeller chamber portion and being shaped to force liquid axially thereof from the intake passage portion toward the discharge passage portion and then radially thereof into the discharge passage portion, and a plurality of vanes fixed in said housing in said intake passage portion and being arranged so as to impart a prerotation to the incoming water in the direction of rotation of the impeller, said housing being also provided with an induction passage leading from the front end of the housing rearwardly and joining the discharge passage portion of said fore and aft channel, the wall of said induction passage adjacent said intake passage portion being curved rearwardly toward the axis of said induction passage so as to cause .water pressure on such wall to be less than the static pressure of the water.

8. A propulsion unit for boats comprising a motor, a housingadapted to be submerged in the water, said housing having a stepped fore and aft channel extending therethrough including a vertically extending impeller chamber portion, an intake passage portion extending forwardly therefrom and a discharge passage portion extending rearwardly therefrom, a drive shaft connected to said motor, an impeller mounted on said drive shaft in said impeller chamber portion and being of the mixed flow type so as to force liquid axially thereof from the intake passage portion toward the discharge passage portion and then laterally away therefrom into the discharge passage portion, and arcuate channel means in said housing in said intake passage portion being arranged so as to impart a prerotation to the incoming water in the direction of rotation of the impeller.

References Cited in the file of this patent UNITED STATES PATENTS 126,639 Leffel M'ay 14, 1872 194,841 Pennington Sept. 4, 1877 387,178 Murphy July 31, 1888 696,666 Berg Apr. 1, 1902 1,075,300 Moss Oct. 7, 1913 1,131,519 Holly Mar. 9, 1915 1,197,181 Buck Sept. 5, 1916 1,267,506 Bowen May 28, 1918 2,000,480 Gorissen May 7, 1935 2,017,302 Yoder Oct. 15, 1935 2,247,817 McMahan July 1, 1941 2,498,910 Camfield Feb. 28, 1950 2,655,891 Gorski Oct. 20, 1953' FOREIGN PATENTS 140,985 Great Britain Apr. 8, 1920 168,333 Switzerland Mar. 31, 1934 

